Fluorinated polymers for corrosion protection of metal

Abstract

The hydrophobic and corrosion resistive film of cross-linked poly(hexafluoroisopropyl methacrylate) was prepared by photopolymerization. The starting materials were a monomer of 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, a photoinitiator of hydroxycyclohexyl phenyl ketone, and a cross-linker of poly(ethyleneglycol diacrylate). Photopolymerization was used to start polymerization and to cure the polymer film on an aluminum surface. Drop-casting was used to deposit the fluoropolymer onto an aluminum substrate (AA 3003). The fluoropolymer film has high corrosion protection when measured by potentiodynamic polarization and open circuit potential techniques in an aqueous solution of 3.5% NaCl. Fourier-transform infrared spectroscopy was used to monitor the polymerization process. The dynamic contact angle technique was used to measure the hydrophobicity for the fluorinated polymer coating. Thermal stability of the fluorinated polymer was measured using thermogravimetric analysis. Treatment with strong acid followed by contact angle measurements before and after the treatment confirmed the chemical resistance for the coated aluminum.

What is claimed is: 
     
       1. A corrosion resistant composition comprising a crosslinked haloalkyl-polymer of formula X: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  are terminal ends of the polymer; 
 R 3  and R 4  are branched or unbranched —(C 1 -C 6 )haloalkyl; 
 R 5  and R 6  are branched or unbranched —(C 1 -C 6 )alkyl; and 
 m and p are each independently at least 10; 
 wherein the ratio of the haloalkyl-monomer moiety and polyethyleneglycol-monomer (PEG-monomer) moiety is about 8:1 to about 10:1, and the crosslinked haloalkyl-polymer is bonded to the surface of an etched metal; 
 wherein the haloalkyl-monomer moiety is 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFiPMA) or 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA); and 
 the PEG-monomer moiety is poly(ethyleneglycol diacrylate) wherein n is about 100 to about 100,000. 
 
     
     
       2. The composition of  claim 1  wherein m and p are each independently about 100 to about 100,000. 
     
     
       3. The composition of  claim 1  wherein the etched metal is aluminum alloy or steel. 
     
     
       4. The composition of  claim 1  wherein the etched metal is aluminum alloy 3003 having a weight percent of 1.5% magnesium, 0.7% iron, 0.6% silicon, 0.2% copper, 0.1% zinc, and 96.9% aluminum. 
     
     
       5. The composition of  claim 1  wherein the etched metal is an alkaline base or plasma etched metal. 
     
     
       6. A method for forming a corrosion resistant composition according to  claim 1  comprising:
 a) mixing the haloalkyl-monomer, polyethyleneglycol-monomer, and photoinitiator, wherein the mole ratio of the haloalkyl-monomer and the polyethyleneglycol-monomer is about 8:1 to about 10:1; 
 b) irradiating the mixture with a sufficient amount of UV light to form a gel; 
 c) applying the gel to the surface of an etched metal substrate; and 
 d) irradiating the applied gel with another sufficient amount of UV light to cure the gel wherein in the cured gel is a solidified crosslinked haloalkyl-polymer that has bonded to the etched metal substrate; 
 wherein the corrosion resistant composition is thereby formed. 
 
     
     
       7. The method of  claim 6  wherein the etched metal substrate is aluminum alloy or steel. 
     
     
       8. The method of  claim 6  wherein the etched metal substrate is aluminum alloy 3003 having a weight percent of 1.5% magnesium, 0.7% iron, 0.6% silicon, 0.2% copper, 0.1% zinc, and 96.9% aluminum. 
     
     
       9. The method of  claim 6  further comprising etching a metal substrate with alkaline base or plasma to form the etched metal substrate wherein the etched metal substrate has an activated surface. 
     
     
       10. The method of  claim 6  wherein the crosslinked haloalkyl-polymer has a thickness of about 1 micrometer to about 100 micrometers. 
     
     
       11. The method of  claim 6  wherein the sufficient amount of UV light or the other sufficient amount of UV light is provided in about 1 minute to about 60 minutes. 
     
     
       12. The method of  claim 6  wherein the crosslinked haloalkyl-polymer is a crosslinked haloalkyl-polymer of formula I or formula II: 
       
         
           
           
               
               
           
         
         wherein
 R 1  and R 2  are terminal ends of the polymer; and 
 m and p are each independently at least 10; 
 n is about 100 to about 100,000; and 
 
       
       the etched metal substrate is an aluminum alloy. 
     
     
       13. A corrosion resistant composition comprising a crosslinked fluoropolymer of formula I or formula II: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  are terminal ends of the polymer; 
 m and p are each independently at least 10; and 
 n is about 100 to about 100,000; 
 wherein the ratio of the polyfluorinated monomer moiety and polyethyleneglycol-monomer moiety is about 8:1 to about 10:1, and the crosslinked fluoropolymer is bonded to the surface of an etched aluminum alloy. 
 
     
     
       14. The composition of  claim 13  wherein the composition has a relative open circuit potential (OCP) value greater than or about equal to 0.3V higher than bare aluminum alloy after the composition and bare aluminum alloy have been immersed for 60 days in a 3.5 wt. % NaCl aqueous solution. 
     
     
       15. A corrosion resistant composition comprising a crosslinked haloalkyl-polymer of formula X: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  are terminal ends of the polymer; 
 R 3  and R 4  are branched or unbranched —(C 1 -C 6 )haloalkyl; 
 R 5  and R 6  are branched or unbranched —(C 1 -C 6 )alkyl; 
 m and p are each independently at least 10; and 
 n is about 100 to about 100,000; 
 wherein the ratio of the haloalkyl-monomer moiety and polyethyleneglycol-monomer (PEG-monomer) moiety is about 8:1 to about 10:1, and the crosslinked haloalkyl-polymer is bonded to the surface of an etched metal.